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ppmtoacad - convert portable pixmap to AutoCAD database or slide
ppmtoacad [-dxb] [-poly] [-background colour] [-white] [-aspect ratio] [-8]
[ppmfile]
Reads a portable pixmap as input. Produces an AutoCAD
slide file or binary database import (.dxb) file as output. If no ppmfile
is specified, input is read from standard input.
- -dxb
- An AutoCAD binary
database import (.dxb) file is written. This file is read with the DXBIN
command and, once loaded, becomes part of the AutoCAD geometrical database
and can be viewed and edited like any other object. Each sequence of identical
pixels becomes a separate object in the database; this can result in very
large AutoCAD drawing files. However, if you want to trace over a bitmap,
it lets you zoom and pan around the bitmap as you wish.
- -poly
- If the -dxb
option is not specified, the output of ppmtoacad is an AutoCAD slide file.
Normally each row of pixels is represented by an AutoCAD line entity.
If -poly is selected, the pixels are rendered as filled polygons. If the
slide is viewed on a display with higher resolution than the source pixmap,
this will cause the pixels to expand instead of appearing as discrete lines
against the screen background colour. Regrettably, this representation
yields slide files which occupy more disc space and take longer to display.
- -background colour
- Most AutoCAD display drivers can be configured to use
any available colour as the screen background. Some users perfer a black
screen background, others white, while splinter groups advocate burnt ocher,
tawny puce, and shocking grey. Discarding pixels whose closest AutoCAD
colour representation is equal to the background colour can substantially
reduce the size of the AutoCAD database or slide file needed to represent
a bitmap. If no -background colour is specified, the screen background colour
is assumed to be black. Any AutoCAD colour number may be specified as the
screen background; colour numbers are assumed to specify the hues defined
in the standard AutoCAD 256 colour palette.
- -white
- Since many AutoCAD users
choose a white screen background, this option is provided as a short-cut.
Specifying -white is identical in effect to -background 7.
- -aspect ratio
- If
the source pixmap had non-square pixels, the ratio of the pixel width to
pixel height should be specified as ratio. The resulting slide or .dxb file
will be corrected so that pixels on the AutoCAD screen will be square.
For example, to correct an image made for a 320x200 VGA/MCGA screen, specify
-aspect 0.8333.
- -8
- Restricts the colours in the output file to the 8 RGB shades.
All flags can be abbreviated to their shortest unique prefix.
AutoCAD
has a fixed palette of 256 colours, distributed along the hue, lightness,
and saturation axes. Pixmaps which contain many nearly-identical colours,
or colours not closely approximated by AutoCAD's palette, may be poorly
rendered.
ppmtoacad works best if the system displaying its output supports
the full 256 colour AutoCAD palette. Monochrome, 8 colour, and 16 colour
configurations will produce less than optimal results.
When creating a .dxb
file or a slide file with the -poly option, ppmtoacad finds both vertical
and horizontal runs of identical pixels and consolidates them into rectangular
regions to reduce the size of the output file. This is effective for images
with large areas of constant colour but it's no substitute for true raster
to vector conversion. In particular, thin diagonal lines are not optimised
at all by this process.
Output files can be huge.
AutoCAD Reference
Manual: Slide File Format and Binary Drawing Interchange (DXB) Files, ppm(5)
John Walker
Autodesk SA
Avenue des Champs-Montants 14b
CH-2074 MARIN
Suisse/Schweiz/Svizzera/Svizra/Switzerland
- Usenet:kelvin@Autodesk.comFax:038/33 88 15Voice:038/33 76 33
Permission
to use, copy, modify, and distribute this software and its documentation
for any purpose and without fee is hereby granted, without any conditions
or restrictions. This software is provided ``as is'' without express or implied
warranty.
AutoCAD and Autodesk are registered trademarks of Autodesk, Inc.
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